1. Field of the Invention
The present invention relates to a technology for allowing hearing-impaired people to distinguish a caller/receiver's voice clearly in telephone conversations.
2. Description of the Related Art
Hearing-impaired people are people who, without the help of hearing aids, are unable to hear, or encounter difficulties with hearing, high-frequency sounds. People with mild hearing-impairment are unable to hear sounds over 6000 Hz. People with severe hearing impairment are unable to hear sounds over 2000 Hz. For these people, sounds of frequencies higher than 4000 Hz cannot be heard even if the sound has been amplified. Since the frequencies of many consonants are higher than 4000 Hz, hearing aids are applied to compress the frequency of the sounds and amplify the sounds for hearing-impaired people. Hearing aids are designed to allow hearing-impaired people to set some sound modification parameters according to their individual audiograms. These sound modification parameters often involve frequency adjustment and sound amplification performed by a modification processing program, in the form of software or firmware, in the hearing aid.
When hearing-impaired people have a face-to-face conversation with other people, the hearing-impaired people can hear high-frequency sounds because those high-frequency sounds are compressed or shifted by their hearing aids. However, during telephone conversations, hearing-impaired people cannot distinguish sounds properly, especially sounds with consonants and short sounds, such as “sit” and monosyllabic words (words with only one vowel sound). This is particularly problematic during telephone conversations conveyed by a landline because high-frequency sounds are removed by the landline telephone before transmission. No sounds with frequencies higher than 4000 Hz are transmitted to the hearing-impaired people.
Some Internet phones remove high-frequency sounds as well; thus, the same problem mentioned above occurs when hearing-impaired people talk with others through Internet phones.
To sum up, hearing-impaired people need help when they are talking on the telephone, and especially on landline telephones.